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SCI2 Transmit Problem After Rx

Mark McDonnell
Prodigy 130 points
Other Parts Discussed in Thread: HALCOGEN

Hi All. I've tried to implement the serial port example that Anthony Vaughan demonstrated in a Youtube video here: 

I'm using the TMS570LS20x USB Stick Development Kit, so I've adapted the example to work on the Lin 2 port. What I've found is that the program works correctly at first. It transmits "Please press a key." I then send a character to the Rx line, and the Tx line goes low. When the dev kit sends the character out the Tx line, it is not understood, I'm guessing because the line doesn't start in the correct initial state. In these captures, I'm receiving then sending the / character. Channel 2 is Rx, and Channel 1 is Tx.

Neither PuTTY, nor the scope can understand the response.

I've tried different drive tx configurations in HALCoGen, but the result is the same. I'm using HALCoGen 4.05.02, and CCS 6.1.2. The project is attached. What am I doing wrong?

1055.Serial-Port.zip

  • 0
    TI__Guru**** 191846 points

    Hi Mark,

      Did you have a chance to use the UART example code  provided by the HalCoGen?

      Another note is that TMS70LS20x is in NRND ((not recommended for new design) state. It is still supported but it is being replaced by TMS570LS31x. If you are creating a new design please consider migrating to TMS570LS31x/21x family.

    Not Recommended for New Designs (NRND)

    Replaced By TMS570LS3137 – The device has the SAME FUNCTIONALITY as the compared device, but is not pin-for-pin equivalent and may not be parametrically equivalent. 

    TI does not recommend using this part in a new design. This product continues to be in production to support existing customers.

  • 0 in reply to Charles Tsai
    Prodigy 130 points
    That's good advice Charles. I'll order a newer dev kit.

    I investigated a little further, and I found that if I use release mode, everything works perfectly. It seems that in debug mode, CCS stops execution just as the micro starts to transmit. In release mode, execution continues.

    Should I consider this solved? Is CCS working as expected? Is this related to use of interrupts?
  • 0 in reply to Mark McDonnell
    TI__Guru**** 191846 points

    Hi Mark,

      I don't know why the debug mode will give the problem but not the release mode. The release mode normally has the optimization set to 2 while the debug mode does not have optimization. Some symbols could be removed with optimization. 

      I wonder if you were placing any breakpoints or watchpoints while debugging the project when in debug mode?